Composite steel/concrete columns which can withstand very important tensile and compressive forces are already known in prior art. Thus it is already known to fill a tube or the free space of an H-shaped steel beam with concrete to increase its compression strength. Such columns are described in U.S. Pat. Nos. 3,050,161 and 4,196,558.
Also known in prior art, there are fire-resistant concrete and steel structural elements which comprise a steel beam covered with concrete to increase the fire resistance of the steel. Examples of such prior art beams are given in U.S. Pat. Nos. 3,516,213; 4,571,913 and 4,779,395.
The following documents are other examples of prior art steel/concrete columns: U.S. Pat. Nos. 915,295; 918,643; 1,813,118; 2,618,148; 2,844,023; 2,912,849; 3,147,571; 3,267,627; 3,300,912; 3,590,547; 3,798,867; 3,890,750; 3,916,592; 3,938,294; 4,128,980; 4,407,106; 4,722,156; 4,783,940; 5,012,622; 5,119,614 and 5,410,847.
A drawback commonly experienced with the known high strength composite steel/concrete columns is that the steel portion of the column which is obtained from a single steel section is still very important as compared to the concrete portion rendering such column not very interesting as far as prices are concerned. Another drawback with such heavy steel sections used with prior art composite columns is that heavy and costly equipment is required to erect those sections on the construction site, as the sections are not easy to manipulate due to their heavy weight.